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FirstStars - Review Questions what do multipoles L tell us...

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Review Questions: -- what do multipoles, L, tell us about the CMB? -- why is the CMB a near-perfect black-body? -- what kind of universe do we live in? -- how are Type Ia supernovae used in cosmology? -- what have they told us about the expansion history of the universe? -- how are supernovae related to the discovery of dark energy? (what affect does dark energy have on the universe?) -- in a v. simple universe, where the expansion rate had always been the value it has now, what is the age of the universe in terms of Ho? -- why are measurements of the CMB so important for cosmology?
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The First Stars Astr 2340 Spring 2010 R. Chandar
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What are the “first” stars? Stars that we see in galaxies are generally classified as either Population I or II However, different lines of evidence suggest that there must have been an even earlier generation of stars than those that are observed in galaxies today These “first” stars, referred to as Population III stars, formed soon after the Big Bang (~100 million yrs) according to simulations We have never seen a Population III star!
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Abundances of Stars: Galactic Variations Disk: Pop I stars, metal rich Bulge: Mostly Pop II stars, metal poor, some Pop I stars Halo: Mostly Pop II stars, metal poor, globular clusters Globular clusters What does this tell us about the chemical evolution of the galaxy?
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Abundances of Stars: Galactic Variations Pop III stars only of Hydrogen and Helium. Supernovae explosions pollute proto- galactic cloud with some metals t = 0 H, He, some metals Formation of Pop II halo stars and globular clusters t = t 1
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Abundances of Stars: Galactic Variations Disk stars are the last to form, thus metal rich Globular clusters were the first to form, thus metal poor. t = t 2
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Population II abundances: Globular Clusters Standard picture: Universe started out with Hydrogen and Helium, stars formed converting this to heavier elements supernovae explosions pollute the interstellar medium with heavier elements. The next generation of stars have a
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